1. Field of the Invention
This invention relates to an improved process for the production of a high concentrated acrylamide aqueous solution by biological hydration of acrylonitrile.
2. Description of the Prior Art
For the production of acrylamide, catalytic hydration methods have hitherto been known in which acrylonitrile is reacted with water in the presence of a catalyst, such as a copper-based catalyst, to produce acrylamide.
This catalytic hydration method, however, has disadvantages in that the preparation of such a catalyst is complicated, the reaction temperature (generally as high as 80.degree. C. to 140.degree. C.) can cause side-reactions such as polymerization, and in that by-products formed by such side-reactions and impurities eluted from the catalyst contaminate the product acrylamide, reducing the quality thereof and making it difficult to produce high molecular weight polymers of acrylamide. For the removal of such impurities, expensive purification techniques using active carbon, cation exchange resins, anion exchange resins, etc. are required.
Recently a process for producing acrylamide from acrylonitrile by the enzyme reaction using microorganisms belonging to the genera Bacillus, Bacteridium in the sense of Prevot, Micrococcus and Brevibacterium in the sense of Bergey has been disclosed, in U.S. Pat. No. 4,001,081, and another process has also been proposed for the production of acrylamide from acrylonitrile by use of microorganisms belonging to the genera Corynebacterium and Norcardia, as described in Japanese Patent Publication (OPI) No. 129190/79 (The term "OPI" as used herein refers to a "published unexamined Japanese patent application".).